Breadth - Structural Engineering Flashcards
what is a tributary area?
a tributary area is a smaller piece of a girder or panel
what is a windload?
it is a load applied to vertical surfaces. for leeway loads it will act upwards
what is a snow load?
a snow load is a load that is a uniformly distributed load and a vertical load
what is ASD?
ASD is the allowable stress design method for loads and they are simply added together
what is the LRFD?
the LRFD is loads that have factors that need to be multiplied
what makes a stable structure?
it is a structure that may bend or deflect and should not move
what are common internal instability structures?
3 hinges in a row in a beam or a frame, parallel or concurrent forces in a determinant truss, and and structure that is not satisfied
what values do you need to know in order to find determinancy?
you need to know the number of members, joints, reactions, and connections
what determines a joint?
a joint in a stability problem is where reactions happen
what are the 2 different methods to find members and forces within a truss?
you can find the forces of trusses by method of joints or cutting the truss in half
what are zero force members?
zero force members are members in the truss that have no force in them
what are the rules of the zero force members?
if only 2 members are connected to a joint, with no external force then both members are F=0, if 3 members are connected to a joint, 2 collinear and 1 non linear then the colinear members are F=0, AND if FOUR members are connected at a joint w/o external force and collinear in pairs then the forces in collinear members are equal
what is a compound truss?
2 simple trusses connected by 3 non parallel bars
what are building frames?
they are like trusses except they are indeterminate and are like braced structures
what is the hack to solving frame problems?
because frames are braced and resist tension so you can remove a brace and find the forces since that allows it to become determinant
what does the value of zero in shear diagram mean?
where shear is zero on a diagram then that means that at that point the greatest moment occurs
when shear is linear what does that say about moment diagram?
the moment diagram will be parabolic
what is the shear stress formula?
shear stress is t=v/a
v = shear force and A = area
what is poisson’s ratio?
poissons ratio is a formula used to find the axial force in the x-direction
v= - (strain y direction) / (strain x direction)
where is the neutral axis?
the neutral axis is located at the center of the section
what is the first step when dealing with a nonsymmetric shape?
find the neutral axis by breaking down the shape and using sum of y = (sum y*A)/sum of A
what happens when a shape is not located on the main axis’?
remember to use the parallel axis theorem
what is the formula for the max moment for a distributed load on a beam?
w=wl^2/8
what is the formula for the max moment for a point load on a beam?
w=p*L/4
what is Q in shear diagrams
Q=y (bar)*A
Q is the area at a certain section in the beam
what is shear flow?
shear flow is needed to calculate shear stress. this can also be used to find the nails and the connectors
what can nails/studs/glue do along beams?
nails can resist the shear stress that happens along the beam.
what is the formula for max shear?
3V / 2A
3/2* average shear
the maximum torsion occurs where along a circular shaft?
the maximum torsion occurs at the outer most radius of the shaft
when given an inclined force on a beam, how should you draw the force on a FBD?
draw the force perpendicular to the beam and the force should equal psin(x)
what is steel good at resisting?
steel resists tension
what is balanced condition in steel design?
when concrete crushing and steel yields at the same time
what is tension control in steel design?
this is when concrete doesn’t fail BUT steel does
what is compression control in concrete design?
its when there isn’t enough steel and concrete fails but steel can’t yield due to its small amount
what is the difference between nominal flexural design and design flexural strngth?
nominal flexural strength has a design factor that has to be multiplied to it
when putting steel reinforcement in a cantilever beam where should the steel be located at?
steel should be placed at the top of the beam
what are the limits for steel ratio that it cannot exceed?
the steel ratio cannot be less than 0.01 nor greater than 0.08
what kind of forces make up internal forces?
internal forces include shear, axial, and moments
how do you find the resultant of a force?
square the force in the x direction and the force in the y direction
what makes a structure stable?
no less than 3 reaction components and there are more known reactions than unknown
when find reactions about structures what should we do with hinges?
when hinges are given for problems it is important to remember that they have internal axial forces
what does a beam experiencing positive bending look like?
its ends are bending upwards and it looks like a smile
when a moment diagram’s drawing goes below the x axis what does that say about the tension?
it’s positive tension
how do you do a shear and bending moment diagram when a part of the structure is on an incline?
you would also draw the inclined portion on an incline, but only the inclined portion
what does a beam deflection depend on?
it depends on loading and member length, geometric properties of areas, and material properties
what is the meaning of the first derivative for deflection equation?
it is the slope for deflection
why do we find the internal forces of a truss if it isnt necessary for design?
finding the internal forces will allow is to see where buckling could occur and reduce the effective length
in thermal expansion/shrinkage problems what does an increase in temperature do to members?
an increase in temperature leads to the member expanding
in thermal expansion/shrinkage problems what does an decrease in temperature do to members?
it shrinks the member
What is the shear stress of a rectangular section?
Tmax = 1.5 v/a
What is the shear stress of a circular section?
Tmax = (4/3) V/A
What is the flexural stress of an I beam?
T Ave = (V / Thickness * width * depth)
what is the formula for torsion?
the formula for torsion is T = (Moment / Ip) * r
when dealing with the eccentricity of footings, what can the effective length not exceed?
eccentricity cannot exceed L/6
what is the moment area method and when is it used?
the moment area method is M/EI and its used when you have 2 different composite sections on a cantilever beam and you need to find the deflection of the beam as a total
for normal weight concrete exposed to freezing and thawing with a maximum aggregate size of 1 in what is the total air content for the mix?
6%
what are the 2 types of most common structural steel that is used?
structural carbon steel (A36) and high strength (A572)
on a stress-strain curve, what happens to the material up until the proportional limit?
the curve is linear and any deformation that occurs during this will be elastic (temporary)
where does the elastic point turn to a plastic point?
at the elastic limit
what is the modulus of elasticity? think graph
it is the slope of the curve in the elastic linear zone
what key property does the stress strain curve reveal about the steel?
the stress strain curve reveals how much energy can be absorbed before it fails
how does carbon affect steel?
it can increase yield strength, reduce fracture strain and toughness, and it does not affect the modulus of elasticity
what does the Charpy V-notch test test for?
it measures toughness and it measures the energy it takes to notch a v into the specimen
how does temperature affect the charpy v-notch test?
temperature is varied during this test because energy varies with temperature
what is welding??
welding is a process to join metal pieces by applying heat to fuse them together
how does steel corrode?
steel corrodes when there is a transfer between electrons in iron and oxygen
if given the corrosion rate of steel what should you do?
you should add that to the thickness of the steel. multiplying it by the life service
what prevents steel from corroding?
coating zinc and adding epoxy
what is cathodic protection?
it is metal (higher than iron) that is sacrificed so that when corrosion can exist it was give up its electron to no longer corrode the steel
what is fatigue?
it is the weakening of a material caused by repeatedly changing the intensity or direction of loads
what members will have to be applied to the parallel axis theorem?
the only members that will have to be applied to the parallel axis theorem are the members that do not cross through the neutral axis.
ie for an I beam only the top and bottom flanges would be applied to the parallel axis theorem BUT you would still find the moment of inertia for the stem portion of the beam
can you explain the Q formula in the first moments of the area formula?
so Q is the moment of the area of the point either above or below the neutral axis. you will split the beam into sections and multiply it by the centroid of the area
what is the formula for deflection angle?
arc length * (I/2L)
or I * C/L
